Existing batch solar water heaters generally comprise a vessel made of glass, metallic or polymeric material that can contain water and may further be constructed of an energy absorbent colored material. Disadvantages of present designs include the fact that many are bulky and made of expensive materials, and still others are inefficient at recruiting, transferring and adequately storing sufficient heat to achieve temperatures adequate to achieve pasteurization. Moreover, many of the current designs are not capable of achieving temperatures required for pasteurizing water.
The majority of diseases in developing countries today are infectious diseases caused by bacteria, viruses, and other microbes which are shed in feces (e.g., human and animal feces) and found in polluted water which people use for drinking or washing. When people drink the live microbes, they can multiply, cause disease (such as diarrhea), and be shed in feces into water, continuing the cycle of disease transmission.
Worldwide, unsafe water is a major problem. An estimated one billion people do not have access to safe water. It is estimated that diarrheal diseases that result from contaminated water kill about 5 million people and cause about 900 million episodes of illness each year. In developing countries city water systems are less reliable, and water from streams, rivers and some wells may be contaminated with pathogens carried by human and animal feces and pose a health threat. For the billion people who do not have safe water to drink the only major recommendation is to boil the water, sometimes for as long as 10 minutes. It has been known since the time of Louis Pasteur (more than 130 years ago) that heat of boiling is very effective at killing all microbes which cause disease in milk and water. However, boiling is not uniformly practiced. Reasons for this include the facts that boiling takes too long, boiled water tastes bad, and fuel is often limited or costly.
There are a number of different disease microbes found in water, but for the most part, they are not unusually heat resistant. For example, the most common causes of acute diarrhea among children in developing countries are the bacteria Escherichia call and Shigelia and the Rotavirus group of viruses. These are rapidly killed at temperatures of 60° C. or greater. For example, heating water to 65° C. in a solar cooker will provide enough heat to pasteurize the water and kill substantially all disease causing microbes. The fact that water can be made safe to drink by heating to this lower temperature (i.e., 65° C.) instead of 100° C. (boiling) presents a real opportunity for addressing the problem of contaminated water in developing countries. However, solar water pasteurizers are often cumbersome and difficult to operate.
Accordingly, there exists a definite need for a portable solar water pasteurizer that is efficient and that is capable of heating water to a temperature and for a time that results in pasteurization, thereby providing a ready supply of potable water. The present invention satisfies these needs and provides further related advantages.